The invention relates to a method for starting up a fuel cell, wherein hydrogen is introduced into an anode chamber of the fuel cell, and at the beginning of the start-up process oxygen is present in the anode chamber of the fuel cell. The invention also relates to a fuel cell system.
During the operation of a fuel cell from the prior art, hydrogen and oxygen are electrochemically converted to water with the aid of a catalyst, which contains platinum applied to carbon particles. When starting up a fuel cell, oxygen can initially be present in a cathode chamber and in the anode chamber of the fuel cell. If hydrogen is now introduced into the anode chamber, a sharp hydrogen/oxygen gas front then develops within the anode chamber, wherein the hydrogen previously introduced is situated in a front region of the fuel cell in the anode chamber and oxygen is situated in the entire cathode chamber and in the anode chamber in a rear region of the fuel cell.
C. A. Reiser et al. describe in “Electrochemical and Solid-State Letters”: 8 (6) A273-A276, 2005 the electrochemical processes of a fuel cell in such a state. In the front region of the fuel cell, the hydrogen of the anode chamber can electrochemically react at an anode to form water and the oxygen of the cathode chamber can electrochemically react at a cathode to form water. Due to the high conductivity of the electrodes, the potentials of the anode and the cathode are approximately constant over the front and the rear region. The low conductivity of the electrolyte in comparison to the electrodes has the effect that a high potential difference is present between the cathode and an electrolyte in the rear, oxygen rich region of the fuel cell. In the rear region of the fuel cell, oxygen is now reduced to water at the anode, whereas carbon of the catalyst is oxidized to carbon dioxide with the aid of water at the cathode. As a result, the catalyst loses its effectiveness and the fuel cell degrades. According to Reiser, this process is referred to as the “reverse current decay” mechanism.